1. Field of the Invention
The present invention relates to a gear for use in gear transmission systems built in vacuum environment such as in space.
2. Description of the Related Art
In the case of this gear intended to use in vacuum environment, its gear body must be usually made of stainless steel, nitrided steel or others having a relatively long life even if it is used together with its paired one without any lubricating matter. This is because the space in which it is used is vacuum and also because the use of any lubricating matter such as grease is difficult there. Particularly when it is used in the field of space development, a solid lubricating film consisting of mainly gold, silver, molybdenum disulfide or others must be formed on those teeth of it which will be engaged with teeth of its paired gear to keep them lubricated while they are turning. This is because it is quite difficult to check and maintain them and also because it is required that they will be highly durable under vacuum circumstances and against high load added and that they will not contaminate any other components at their peripheral region.
Machines and devices which will be launched into space by the spacecraft have been made larger and larger in size these days in the field of space development. As they become larger in size, load unexpectedly higher is sometimes added to the gear transmission system at the drive section for their space manipulators, for example. It is therefore required that those gears which will be used as components of the gear transmission system in space can be kept reliably operative for a long time under this unexpectedly high load added.
When high load is added to the above-described gears, however, their solid lubricating films become liable to separate from each other, thereby making it difficult to keep them reliably operative for a long time.